1. Technical Field
This disclosure relates generally to catalyst systems, and, more particularly, to diesel oxidation catalyst (DOC) systems substantially free of Platinum Group Metals (PGM).
2. Background Information
Regulatory standards for acceptable emissions may be continuously revised in response to human health issues and air-quality concerns. Strict-compliance regulatory standards may be adopted worldwide to control emissions of oxides of nitrogen (NOx), particulate matter (PM), carbon monoxide (CO), and carbon dioxide (CO2) from various sources, such as automobiles, utility plants, and processing and manufacturing plants amongst others, prior to exhaust gas discharge to the atmosphere. Exhaust gases of CO, HC, and NOx may be one of the main objectives for catalytic control of air pollution.
Diesel oxidation catalyst systems may be manufactured using platinum group metals (PGM) which are characterized by a small market circulation volume, constant fluctuations in price, and constant risk to stable supply, variables that drive up their cost. These facts may be conducive to the realization of a PGM-free diesel oxidation catalyst system.
A need may exist for diesel oxidation catalyst systems which may not require PGMs and may have similar or improved performance as currently known diesel oxidation catalyst systems. Said catalyst systems may face the need of upgrading their resistance to catalytic poisons because the surface of metallic nano-particles in the catalytic centers may show affinity to other chemical species that when adsorbed may block the adsorption of the target species of the catalyst, causing a serious suppression of the desired reactions. This suppression of reactions may take place even with overheating of the catalyst materials at regular intervals to promote thermal desorption of catalytic poisons from the catalytic center surface and to reactivate the catalytic function. The problems faced by PGM catalyst systems may be addressed by alternative materials which may be used as active catalyst phases. Among these materials, perovskite oxides may be alternatives for exhaust gas depollution.
For the foregoing reasons, it may be desirable to have a cost effective diesel oxidation catalyst system, which may control exhaust emissions with similar or enhanced catalytic performance than existing diesel oxidation catalysts.